Hydraulically synchronized servo system control



p 1947- E. DAWSON 2,426,986

HYDRAULICALLY SYNCHRONIZED SERVO SYSTEM CONTRDL Filed May '17, 1943 I 4 Sheets-Sheet 1 REFERENCE MEMBER) FlGZ EXHAUST FIG.

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' INVENTOR EDWARD DAWSON BY Mun 7 ULIOALLY smcmzomzzn sanvo svs'm coumoz.

4 Sheets-Sheet 4 INVENTOR W AWSQN HIS ATTQR E. DAWSON I 2,426,986

2,426,5986 RAULECALLY SYNQHRONKZED SERVQ SYSTEM (I! Edward Dawson, New York, N. Y assignor to Sperry Gyroscope Company, llna, a corporation of New Yorlr ONTROL Application May 17, 1943, Serial No. 487,395

My invention particularly relates to, a control system for servomotors computer systems and in which coarse and fine fluid control valves are employed to control both the'direction and rate of operation of the associated servomotor.

In control systems of this character, the line control valve is operative to control the servo when the error angle between a reference memher and the element positioned or driven by the servo does not exceed some predetermined value, while for all other, larger values of error-angle the servo is controlled by the coarse valve. rdinarily, the coarse and fine valves are operated in relatively unequal but constant ratio relationship with respect to the reference member, and the operations thereof may be effected through Selsyn systems and associated gearing. For example, angular movement of the valve element of the coarse valve may take place in a 1:1 ratio with respect to the reference member, while that of the valve element of the fine valve may take place in a :1 or 27:1 ratio, or in any suitable odd, preferably composite number, ratio.

A synchronizing device is employed to render the fine control valve inefi'ective in its control over the servomotor and to connect the servo motor directly with a source of iiuid under pressure when the error angle exceeds a predetermined value. Under this latter condition, while the coarse valve, through the synchronizer, control the direction in which the servomotor is driven, the servo will operate atmaximum rate.

The synchronizing device, one of the novelfeatures of this invention, functions to return the control of the servomotor to the fine control valve when. and only when, the element driven and positioned by the servo lies within the predetermined maximum error angle with respect to the position of the reference element.

It is an object of my invention to provide a control system for servomotors in which coarse and fine control valves are employed and in which a hydraulically operable synchronizing device is incorporated.

It is another object of this invention to provide .a novel form of hydraulic synchronizer. A still further object resides in providing a hydraulic particularly useful insynchronizer which, under the control of a valve,

is operable to connect either end of a hydraulic motor to a source of fluid under pressure and the other side thereof to exhaust, depending upon the operation of the valve controlling the same, and which is otherwise operable operatively to connect a second control valve in controlling relation to the servomotor.

Another object resides'in providing a hydraulic synchronizer of the foregoing character which is so constructed and arranged that movement of the valve elementsthereof from one position to another will take place very rapidly following an initial movement thereof.

Still another object resides in providing a novel fluid control valve which may be employed either as the coarse or the line control valve in a hydraulic system.

Another object lies in providing a control valve which is characterized by the fact that the rotatable valve elementtherewithin may be operated by torques of comparatively small magnitudes; that the valve element is hydraulically balanced whereby for all operating positions thereof, locking or binding is prevented; and the valve elements may freely rotate under all conditions. It is a further object to provide a hydraulically balanced valve of this character which is simple in construction and may be easily manufactured.

With the foregoing and other objects in view, my invention includes the novel control system and the novel control elements therein contained which are described below and illustrated in the accompanying drawings, in which:

Fig. 1 schematically represents one manner of operatively connecting the coarse and fine control valves of my system with a reference member;

Fig. 2 is a fragmentary, longitudinal section through my novel form of fluid control valve;

Fig. 3 is a transverse'section of Fig. 2 taken in about the plane 33 thereof;

Fig. 4 is a longitudinal section of the outer member of the valve sleeve;

Fig. 5 is an elevational view of the inner member of the valve sleeve;

Fig. 6 is a longitudinal section taken through the inner and outer members of the valve sleeve operatively secured together in fixed relation;

Fig. '2 is a development of the inner sleeve member shown in Fig. 5;

Fig. 3 discloses in part my novel servomotor control system, the valve elements and synchronizer being shown in section;

Fig. 9 discloses the balance of the system shown in Fig. 8, the connecting parts thereof being represented as cut ofi at the dash-dot lines m--a:, 21-y and z-z;

to which it may be actuated; and

Fig. 11 discloses the operational curves of the coarse and fine control valves.

In the embodiment of my invention herein illustrated and particularly illustrated in Fig. 1, I have shown a reference member indicated genorally at l which may be positioned or moved either manually or automatically to provide a positional reference employed in controlling the operation of a servomotor and the positioning thereby of some positionable object or element.

For example, the reference member may be associated with or constitute the data output shaft of a computer system and the positionable object may comprise a turret or plurality of turrets.

In the embodiment shown, the reference member I is directly coupled to the shaft 2 of a transmitter 3, which may be a Selsyn or Autosyn I transmitter 8 is also electrically connected with the source of alternating current feeding the above described transmitter and receiver and is mechanically connected with the rotor of the transmitter 3 through a gear train indicated generally at 9. The gear that the rotor Iv of transmitter 8 will rotate in a ratio of, for example, 2'7 :1 with respect to the rotor of transmitter 3. The stator of the transmitter 8 is electrically connected with the stator of a receiver 10, the rotor of which is electrically connected with the above-mentioned source of alternating current and mechanically connected with the valve element of a second or fine control valve Ii.

From the foregoing it will be observed that the valve element of valve II will havean angular displacement of twenty-seven times that of the valve element of control valve 6 or, in other words, the magnitude of movement of reference member I as reflected in the movement of the valve element of valve II will be magnified twenty-seven times.

In practice, the valves and Ii as shown in Fig. 8 are embodied in one casing, and, in accordance with my invention, may be substantially identical in design and size. The preferred form of my novel fluid control valve is illustrated in Fig. 2 wherein 12 indicates the valve body or casing within which the valve sleeves and rotary valve spools are rotatably mounted. The body I2 is provided with an axially extending bore 13 which, in the embodiment shown, has a sleeve I4 securely fastened therewithin and within which the valve sleeve [5 may be rotatably mounted. Sleeve I4 is provided with openings l6, l1, l8 and I9 which are adapted to register respectively with passages in the valve body l2. In each or to each of these passages is connected conduits 20, 2|, 22 and 23, which are connected in the control system. Within the bore of the sleeve I4 is rotatably fitted a valve sleeve 15 and, as hereinafter described, said sleeve is designed to be oscillated to a small bore of the valve.

The construction of the valve sleeve l5 and its inner and outer component members is best illustrated in Figs. 4 through '7. Referring first to Fig. 4, the outer member of the valve sleeve comprises a generally cylindrical body 24 within which the inner sleeve member 25, shown in Fig. 5, is adapted to be fixedly secured, whereby the two members will move as an integral unit. The outer member 24 is provided with a plurality of axially spaced grooves 25, 21, 28 and 29 which, when operatively mounted within the valve body,

train is so arranged degree axially of the are adapted continuously to register respectively with the passages 15, l1, l8 and IS.

The walls of member 24' are provided with diametrically opposed openings or ports 30which connect with the interior thereof and with the groove 26. Likewise, openings or ports 31 connect between the groove 29 and the interior of sleeve member 24. A single port 32 affords communication between the groove 21 and the interior of the member 24 and, in axial alignment therewith, a single port opening 33 affords communication between the groove 28 and the interior of member 24. A gear 34 may be mounted on the lower end of the member 24 or may be formed integral therewith, as illustrated.

The inner member 25 of the valve sleeve, for purposes which will become apparent as the description proceeds, is designed to be mounted within the outer member 24 and secured thereto to form a unitary structure. The inner member 25 is generally cylindrical and provided with an interior, axially extending bore 35. Axially spaced groves 36 and 31 are adapted when the two sleeve elements are fastened together to lie in communication with the-lateral'ports 30 and 3|,

respectively. Laterally extending ports 38 and 39 afford communication between the grooves 36 and 31, respectively, and the interior of the member 25. The cylindrical surface of the member 25 lying intermediate the grooves 35 and 31 is provided with a pair of grooves indicated generally at 40 and 4|, which grooves extend peripherally of the member 25 slightly in excess of and also axially of said member.

The configuration of grooves 40 and 41 is more clearly shown in Fig. '7. A pair of laterally extending ports 42 and 43 communicate with the interior of the member 24 and with the groove 40 adjacent opposite ends thereof. In other words, the ports 42 and 43 are diametrically opposite each other but spaced axially of the sleeve member 25. Likewise, lateral ports 44 and 45 communicate with the interior of member 25 and exteriorly thereof with the groove 41 adjacent opposite ends thereof. These ports will likewise lie generally diametrically opposite but in axially spaced relation to each other.

The relative association of the inner and outer valve sleeve members when fixed in relation to each other to provide the unitary valve sleeve structure I5 is illustrated in Fig. 6. It will be noted that groove 36 forms an annular passage within the interior of the sleeve connecting the ports 38 with the ports 30. Likewise, the groove 31 provides an interior passage connecting the ports 31 and 39. Furthermore, the groove 40 forms an interior passage connecting the port 32 in the outer sleeve member with the port 43 in the inner sleeve member whereby fluid supplied through the port 32 may be conducted axially of the valve sleeve and interiorly thereof, and discharged through the port 43 to the interior of the sleeve and in a zone diametrically opposite but axially spaced from the port 32. At the same time, the port 42 will lie in communication with the port 32. As hereinafter explained, passage of fluid through the port 42 or port 43 is controlled by a rotary valve spool rotatably mounted within the bore 35 of .the valve sleeve. Similarly, although the passage formed thereby is not illustrated in Fig. 6, the groove 41 connects the exterior port 33 with the interior port 44 and also with the axially spaced interior port 45. Passage of fluid through these latter ports will also be preferred circumferential controlled by rotary valve spool rotatably mounted within the sleeve.

When the valve sleeve l5, comprising the inner and outer members 24 and 25. is operatively and rotatably mounted within the valve casing 82, it will occupy the position shown in Fig. 2 wherein the grooves 26, 21!, 2B and 29 register respectively with the passages it, ll, l8 and id in the relatively fixed valve body. As hereinafter described, means are provided for efiecting a slight axial oscillation of the valve sleeve it and it will be clearly evident that such motion may take place because of the axial extent of the grooves in the exterior of the valve sleeve or their registering passages in the valve body.

Within the valve sleeve is rotary valve spool or dd and comprising the spaced lands 4! and at whichare adapted closely but slldably and rotatrotatably mounted a ably to fit within the valve sleeve l5 and to effect axially spaced closures within the sleeve 65. In termediate. the lands d! and dd, the valve $6 is provided with an enlarged cylindrical portion id which is adapted closely to fit within the bore of the sleeve 65. The enlarged portion 59 is milled, as indicated at 59 and 5!, or otherwise formed to provide a partial cylindrical valving surface adapted to control the flow of fluid through the interior ports of the valve sleeve, adjacent which the valve 56 rotates. By milling the valve member in spaced relation as indicated, a completely cylindrical land 52 will be provided between axially spaced zones of the valving surface. The extent of the valving surface as of the valve spool and the circumferential extent oi the associated interior port openings is clearly illustrated in Fig. 3.

In Fig. 3, the valve spool has been rotated substantially 90 relative to the position thereof illustrated in Fig. 2, and it will be noted that in this position thereof the valving surface of the valve spool prevents flow of fluid between the bore of the valve sleeve i5 and both ports 62 and $5. In this position of the valve, communication between the ports ill and '53 and the bore of the sleeve i5 will likewise be cut oil. Preferably, when the valve spool occupiesthe position shown in Fig. 3 the edges of the valving portion thereof register with one edge of the associated ports so that rotary movements of the valve piston from the illustrated position thereof in either direction will produce substantially instantaneous port openings which progressively increase with greater magnitudes of relative movement of the valve piston and sleeve.

The valve piston it, in the embodiment illustrated, is operatively connected with the rotor of either the coarse or fine Selsyn receiver through suitable couplings which comprise the first coupling element 53 which is secured to the valve piston to by means of pin 5d and a second coupling element 55 which is secured to the rotor of the Selsyn receiver. A helical torsion spring 56 is secured at opposite ends thereof to the coupling elements 53 and 55, respectively, whereby rotary movement of the rotors of the Selsyn receivers are transmitted to the valve pistons of the respective coarse and fine control valves, as clearly illustrated in Fig. 8.

By virtue of the gear train connection between the coarse and line transmitters, the valve piston of the coarse valve will rotate to the same piston indicated generally at mains constant.

angular extent as the reference member while the valve piston of the rotate, for

fine control valve will the values herein assumed, through moved thereby to the rate thereof,

vinder of a strokingpiston;

vides a reference corresponding in some ratio to the reference provided by the reference member. Likewise, the valve sleeves also provide, as hereinafter more particularly described, a reference which is primarily indicative of the movement or position of the positionable element driven by the servo. In other words, assuming that the reference member is displaced at a given velocity, the associated rotary valve spools will be uncover one or more of the associated ports whereby to efiect an operation of the servo to drive its load or positionable element in the same direction asthat in which displacement of the reference member occurs and substantially at the same rate. Hence, when the servo, assuming a stroking piston controls is operating at the rate corre rate of thereference member, port openings in the control valves should be closed and the positionable element will then continue closely to follow the reference member, assuming that its rate re- Hence, movement of the load or positionable element should be reflected in a movement or the valve sleeves and the movements of the respective valve sleeves should bear the same ratio to each other as the movements of their associated valve spools.

In the embodiment illustrated, as shown in Fig. 8, this is accomplished by meshing the gears as associated with each valve sleeve in a gear train including the'gears 5t, 57, 5t, 5t, and gears dd and d9, gears Ed and dd meshing with the gears lid of the valve sleeves and gears 59 and ti meshing with a driving gear 62. The gear ratios of the gear train are so arranged that the sleeve oi the control valve ll will rotate with the sleeve of the valve 6 but through an angular displacement equal to twenty-seven times that of the sleeve of valve t. Obviously, the driving gear 62 is driven in some suitable manner, as hereinafter more particularly described, from a load shaft or its equivalent of the servomotor.

As shown in Fig. 8, the gears at on the valve sleeves rotate between-the spaced discs 83 and at forming a yoke on a shaft 65 which is mounted to reciprocate in a bore 5b in the valve body it. An eccentric bl, driven from some suitable source of power, is connected to the shaft 55 and-serves to oscillate the valve sleeves to a slight extent and axially oi the bores oi the valve in which they are mounted. It willbe noted that the width of the gears Ed and at is sumcient to perunit this slight oscillation.

In considering the operation of these valves, the operation of each being substantially identical, let us assume, considering valve ii, that the conduit 2@ is connected to a source of fluid under pressure; conduit it is connected with one side of a hydraulic motor or the head end of the cylthat conduit 22 is connected to the other side of said motor or the crank and of said cylinder; and the conduit 23 is connected to exhaust or to a suitable sump. When the valve piston occupies the position shown in Fig. 3, fluid under pressure may pass from the conduit 20 through the groove 26 and ports 3%, the interior passage formed by the groove 36 in the valve sleeve and through ports 3 to the bore of the valve sleeve between the spending to the the controlling tive rotation will control the rate at lies in communication with the bore of the sleeve between the lands 48 and 52, this connection being established through the ports 39, groove 31, ports 3| and groove 29.

Assuming that the valve spool rotates to some extent in a counter-clockwise direction relative to the sleeve as viewed in Fig. 3, ports 42 and 44 will be uncovered and to an extent depending upon the degree of such relative movement thereby permitting fluid under pressure to pass from the space between the lands 41 and 52 through the port 42 and port 32 and groove 21 to the conduit 2|, thereby supplying fluid under pressure to one side of the motor or to one side of the stroking piston. Since port 44 is simultaneously uncovered with 'port 42, the space between the lamb 48 and 52 of the valve spool, which continuously communicates with the exhaust conduit 23, will be connected through ports 44 and 33 and groove 28 with conduit 22, thereby connecting the other side of the motor or stroking piston with exhaust. Under the above assumed conditions, fluid under pressure will cause the motor or stroking piston to be operated under fluid pressure supplied to the head end thereof and, in the case of the stroking piston, the rate of movement thereof will depend upon the size of the port opening, and the magnitude of such movement will depend upon the duration of the port opening.

Under the assumed conditions of relative rotation of the valve spool and sleeve, it will be observed that the ports 45 and 43 will be closed by the valving surface of the valve spool. Therefore, fluid cannot flow through these ports. However, if the valve piston is moved in a clockwise direction from the position thereof shown in Fig. 3, the ports 42 and 44 will remain closed but the ports 45 and 43 will be opened to some degree. When this occurs, fluid under pressure within the bore of the valve sleeve and between the lands 4'! and 52 cannot pass to the conduit 2i and the head end of the stroking piston but will pass through the port 45, groove 4| to port 33, the valving surface of the spool closing the port' 44 and thereby preventing escape of fluid therethrough. Fluid under pressure will therefore pass from port 33 and associated groove 28 to the-conduit 22 and thence to the crank end of the hydraulic motor or stroking piston. At the same time, the space between the lands 48 and 52 will be connected through port 43 and groove 40 with port 32, port 42 being closed by the valving surface of the spool from communication with the interior bore of the valve sleeve. But, fluid may pass to groove 40 from port 32 which communicates through groove 21 with the conduit 2i. Hence, the head end of the stroking cylinder will be connected with exhaust. Arrows in full line represent one condition of operation and arrows in dotted line represent a second condition.

Obviously, the direction of relative rotation of the valve piston and valve slee e will determine the direction of operation of the servomotor controlled thereby, and the magnitude or such relawhich the servo is operated. For relative departure of orientation between the reference member and follow-up element, the valve spool and sleeve of both coarse and line control valves will be'relatlvely rotated but, of course, to different mag.- nitudes of extent depending upon the gearing ratios therebetween. The relative operational characteristics of the coarse and fine control valves in terms of angular position of valve sleeve is graphically depicted in Fig. 11 wherein cur've 58 represents the stroking piston rates provided the coarse valve were connected directly to control the stroking piston as above described and it is rotated through 180 in opposite directions toward zero or the point corresponding to synchronized operation of the reference member and positionable element. Curve 69 in a similar manner depicts the stroking piston rates which would be provided by the fine controlyalve if operatively connected continuously to control the stroking piston and when movement thereof corresponding to the above-described movement of the coarse control valve occurs. I

The curve above the axes a-a indicates decreasing angle of sleeve while that below the axes indicates increasing angle of sleeve and, in each case, representing operations of the servo but in opposite directions toward the zero point. It will be observed that between the 180 and 0 points the stroking piston rates, as controlled by' the coarse valve, vary from zero to maximum and back to zero again at the zero position, while the corresponding stroking piston rates, if controlled by the fine control valve vary from zero to a maximum on the decreasing angle side of the curve and back through zero to a maximum on the increasing angle side, and that ,this continues thirteen and one-half times throughout because of the 2'7 :1 assumed ratio.

The manner in which the hydraulic synchronizer shifts control of the servomotor from the coarse or fine control valve to the other will be hereinafter explained, but it will be observed at this point that a much. more accurate control .will be effected if the fine control valve is operatively connected with the servomotor for small error angles than if a coarse control valve alone, having a 1:1 ratio of movement.with respect to the reference member, were employed in its stead.

The hydraulic synchronizing device of my invention is shown in Figs. 8 and 10 and comprises a casing 10 having a pair of axially extending bores Ii and 12. In each of these bores is slidably mounted a valve spool and since they are of substantially identical design an explanation of one thereof is considered sufficient. The valve spool indicated at 13,. which is slidably mounted in the bore H, is provided with a plurality of axially spaced lands 14, I5, 16 and 11. A sleeve 18, within which the piston valve 13 is mounted, is secured within the casing HI and is provided with a plurality of circumferentially extending grooves having diametrically opposed ports therein which communicate between the respectivegrooves and the bore H. A first of said grooves, indicated at 19, is connected through a conduit Bli with the control valve 5. A second groove 8| is connected with a source of fluid under pressure; and a third thereof, groove 82, is connected with exhaust. In the position of the valve spool 13 shown in Fig. 8, fluid under pressure may be supplied through groove 81 and its associated ports to the bore about 70% H and between the spaced lands M and 75 through ports to a groove 83, which is connected through a passage 84 to a groove 85 extending about and communicating through ports with the second bore 12 of the synchronizing device.

The spool 86 slidably mounted in bore 12 is substantially identical with spool 13. Fluid passing from the groove 85 and between the lands 8! and 88 of piston 86 may pass through ports to groove 89 and thence through conduit 20 which is connected therewith and with valve ii. Between the lands and E6 of piston 73 is disposed a pair of grooves 90 and Si, groove 90 being connected with conduit 92 which, as shown in Fig. 9, is connected with the head end of a stroking cylinder 93. Groove 9i communicates with passage 9 3 which in turn communicates with a groove 95 disposed about the valve spool 85 and between the lands 96 and 9? thereof. A second groove 98 disposed between said lands communicates through conduit 2i with the control valve ii.

Conduit 22 which, as above described, is connected at one end with control valve ii is also connected with the synchronizer and communicates with a groove 99 which encircles the spool l3 and lies between the lands it and ill thereof. A second groove ltd also lying between the lands l6 and ii communicates through passage it! with a groove M2 encircling the valve spool '86 and lying between the lands 88 and 96 thereof? A second groove H13 also disposed between the lands 8% and 9t communicates with conduit Hid which is connected to the crank end of the stroking cylinder 93. A groove tilt corresponding to groove 82, above described, encircles the bore '12 and communicates through ports therewith and through passage tilt with groove 82.

The bores ii and 72, as illustrated, are of somewhat smaller diameter at one end thereof as indicated at Bill and ltd, respectively, and pistons ltd and H0 are slidably mounted therein. The diameter of pistons ltd and M0 is preferably of the diameter of the lands of the spools l3 and 86. Fluid under pressure is normally supplied through conduit iii to the space within the zone lll'i of the bore and betweenthe piston we and the end of the casing. A passage H2 between the ends of the bores it'i and ltd, serves to supply fluid under pressure to the space between the piston Md and the adjacent end of the casing. Under these conditions, pistons ltd and i ill serve normally to urge the spools i3 and 86 toward the left, as viewed in Fig. 8, maintain ing the opposite ends of the spools against their associated end walls of the casing.

Preferably, the last-mentioned ends of the spools l3 and as are of frusto-conical form and fluid under pressure may be supplied through the conduit M to the space between the frustoconical end of the spool 73 and the adjacent end of the casing. An orifice M3 is provided in the end of the casing for the exhaust of the fluid so supplied thereto. Fluid may also be supplied through conduit i it which is connected at one end with the valve 6 and at the other end thereof with groove i It which surrounds the spool 58 and communicates through ports with the bore l2 adjacent the frusto-conical end section of the spool 8%. Likewise, an orifice Me is provided for the exhaust of fluid from the end of bore 12.

The positions of the spools i3 and 86 illustrated in Fig. 8 are the positions which'they normally occupy when control over the associated servomotor is exercised by the line control valve.

may pass to the synchronizer and to groove 8! thereof, passing therefrom through groove 83, passage 86, grooves and 89 to conduit 20. Assuming that the fine control valve occupies a position wherein the conduits 2!! and 2| are connected with each other through the valve, full fluid pressure will be present in conduit 20 and its passage therefrom to conduit 2| will be controlled by valve i. Fluid may then pass through conduit 2! back to the synchronizer, through rooves 98 and 95, passage lit-and grooves and 9G to the conduit .92 which is connected with the head end of the stroking piston 93. This will cause the stroking piston ill to move downwardly as illustrated in Fig. 9, and thereby control the A end of a hydraulic transmission indicated generally at H8. The hydraulic transmission herein illustrated is shown mainly for exemplary purposes, and it will be understood that movement of the stroking piston 'to either side of its central or neutral position will ,varythe displacement of the A end and thereby control both the direction and rate of operation of the B end of the unit. The A end is driven by a suitable motor (not shown) and fluid under pressure is supplied through either the conduits H9 or i 20 to the 3" end, being returned through theother of said conduits. The B end E2! of the unit constitutes a hydraulically driven motor and its output or load shaft i22 may be suitably connected to drive a positionable element.

Under the above assumed position of the fine control valve, fluid is supplied therethrough and controlled thereby to the head end of the stroking cylinder til. At the same time, valve 1 M will control the exhaust of fluid from the crank end of the stroking cylinder, fiuid passing through the conduit we to the synchronizer, through grooves W3 and its, passage ml, grooves Hi0 and 9t and thence through conduit 22 to the control valve ii. Fluid may then pass through the valve ii to the exhaust conduit 23. While the pistons it and 86 of the synchronizer remain in the positions illustrated in Fig. 8, the fine control valve it may control the passage of fluid under pressure to either the head or crank end of the stroking cylinder and the exhaust oi fluid from the other end thereof.

Assuming, however, that the angular displace ment between the positionable element driven by the "3 end of the hydraulic transmission or servomotor and the reference member exceeds a predetermined maximum value, the coarse control valve 8, to which fluid under pressure is supplied through the conduit !23, will operate to pass fluid through the conduit 88 and to the space between the frusto-conical end of spool '13 and the adjacent end of the casing Hi. When this error angle exceeds the predetermined value, the port opening in valve 5 will be of such size order as to produce fluid pressure against the conical surface of the end of spool it of the synchronizer sumcient to overcome the force applied to the piston tilt. Initially, this fluid pressure will be exerted only upon the conical sides of the spool i3 and not upon the base thereof which abuts the end of the casing. However, upon an initial movement of the spool 86 to the right as viewed in Fig. 8, fluid pressure will be ex-- erted against the entire end surfaces of thespool and cause it rapidly to move to an alternative position such as thatshown in Fig. 10. When this occurs, fluid under pressure is prevented from passing from the groove M of the synchronizer to the groove 83 and thence through conduit 20 to the control valve II because the land I4 will overlie the port communicating between the groove 83 and the bore II. At the same time, the fluid under pressure from the groove 8I will pass directly to the conduit 82 and to the head end of the stroking cylinder, thereby causing the "B" end of the unit to accelerate to maximum velocity while rendering the fine control valve temporarily ineffective. At the same time, the crank end of the stroking piston will be connected directly to exhaust. In other words, fluid may fiowthrough the conduit I04, grooves I03 and I02, passage IOI, groove I and between the lands I8 and II of piston 13 to groove 82 and thence to exhaust. 1

Likewise, if the fine control valve were controlling the fiow of fluid under pressure to the crank end of the stroking piston and the error angle were to exceed the predetermined maximum value, coarse control valve 0 would operate in a manner similar to that above described to supply fluid under pressure to the space between the frusto-conical end of spool 86 and the adjacent end of the casing of the synchronizer suiiicient to apply a force to the spool 88 causing it to assume a position similar to that of piston 13 illustrated in Fig. 10. When this occurs, the

crank end or the stroking cylinder will be connected directly to the source of fluid under pressure which lies in communication with the groove Ill, and the head end of the stroking cylinder will be connected directly to exhaust. In this assumed position of the spool 86, fluid under pressure will flow from the groove 8i to groove 83, through passage 84 and groove 85 to groove I03 which lies in communication with conduit I04 connecting with the crank end of the stroking cylinder. The head end thereof through conduit 92 is connected with grooves 90 and SI, passage 96, groove 95 and through the space between the lands 36 and 91 with the groove I05 which is connected through passage I06 with groove 82 and exhaust.

In the embodiment of my invention shown in Figs. 8 and 9, the sleeves of the control valves 8 and I I are moved in proportion to the movement of the load shaft I22 of the 3" end of the unit or proportionally to the movement of the positionable member. In the' embodiment shown, this is accomplished through the medium of gear I24 meshing with gear I 25 which is mounted on the drive shaft of the 13" end of the unit. The gear I24' through shaft I26 drives gear I21 which meshes with gear I28 constituting one arm of a differential indicated generally at I29. A second arm comprising the planetary gears of the differential drive shaft I30 on which is mounted bevel gear I3I (see Fig. 8) which in turn meshes with bevel gear I32 mounted on the shaft I33 on which is also mounted the driving gear 62 for the connecting gear train of the fine and coarse control valves. Hence, when the servo motor or hydraulic transmission unit is actuated in one direction or the other, the sleeves of the coarse and fine control valves will be rotated in corresponding directions and the magnitude of operation of the servomotor will also be reflected in the magnitude of rotary movement of the valve sleeves.

For stabilizing purposes, I have provided in theembodiment illustrated a rack I34 which is cperatively connected with the stroking piston II] and engages the third arm or gear I35 of the differential I29. With this arrangement,

when the stroking piston III is moved to contral or adjust the speed of the B end of the servo unit in response to a signal, the resulting motion of the stroking piston is imparted through the differential, shaft I30 and the gear train driven thereby to the sleeves of the valves causing them to follow the position of the rotary valve spool.

By referring to Fig. 11, it will be observed that when the error signal which may be represented or measured by the angular displacement between the rotary valve member and sleeve of the coarse control valve drops below the predetermined maximum for fine valve control, the fluid pressure, controlled by the coarse valve, which exists 'in the synchronizer, will decrease to a value suilicient to permit the spool I3 or 85, as the case may be, to return to the position thereof illustrated in Fig. 8, under the force of fluid pressure applied to the associated piston. The angular displacement of the rotary valve spool and sleeve-when pressure in the synchronizer decreases to a value sufiicient operatively to connect the fine control valve in controlling relation to the servomotor may be indicated at the. point I: on the curve 88. The corresponding point on the curve 69 will lie at point 0. It will be observed that for this position of both the fine and coarse control valves that the curves both lie on the same side of the axes a-a representing a decreasing angle of the sieeve and therefore it is proper at'this point to transfer control from the coarse to the line valve.

If the coarse control valve were to transfer control to the fine control valve at some point 180 removed from the above point, or at a point corresponding to the point d on the curve 69, it will be observed that the fine control valve will be operating on the increasing angle of sleeve valve portion of its curve and would therefore produce a greater angle of error. Therefore, the coarse control valve would again take over control causing the positionable element to be oriented throughout 180 when the coarse valve could again return control to the fine valve at the points 0 and b on the curves. nder these conditions, therefore, synchronization and return of the fine control valve to control over the servo. can only take place when the error angle lies within the predetermined maximum, and ambiguity of 180 cannot result.

Furthermore, it may be observed that the controlling action of the fine control valve, that is, the magnitude of change in port openings for a given change in error angle, is many times larger than the corresponding port opening which would be provided with the coarse control valve, and hence much more accurate control over the servo is effected and a closer following of the positionable element in its movement with that of the reference member.

It will be understood that in the servo system and the servo control system, the operating fluid is preferably oil. Furthermore, hydraulically operable, electrical switches such as that indicated at I36 may be connected in the control system whereby electrically to control a signal device or electrical valves and the like. In the embodiment shown in Fig. 8, switch I30 is connected to conduit 20 and hence will be operated when control is taken away from or restored to I the fine control valve II.

Furthermore, the particular servo system, herein disclosed is intended mainly for exemplary purposes, and the synchronizer may be employed with many different types of servo systems. 7

As many changes could be made in the. above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a hydraulic control system, hydraulically operable motor means, conduit means for supplying to and exhausting fluid from said motor means, a coarse fluid-control valve and a fine fluid-control valve included in said conduit means for controlling the flow of fluid there through, and fluid-pressure responsive means operatively connected with said coarse valve and including means responsive to fluid pressure supplied thereto through said coarse valve for connecting said Iine valve in controlling relation to said motor means and for connecting said motor to a source of fluid under pressure.

2. In a hydraulic control system, hydraulically operable reversible motor means, conduit means for supplying to and exhausting fluid from said motor means, a coarse fluid-control valve and a fine fluid-control valve included in said conduit means for controlling the flow of fluid therethrough, and fluid-pressure responsive means operatively connected with said coarse valve and including means responsive to fluid pressure supplied thereto through said coarse valve for connecting said fine valve in controlling relation to said motor means and for connecting either a first side of said motor means to a source of fluid under pressure and the second side thereof to exhaust or said second side to said fluid source and the first side to exhaust.

3. In a hydraulic control system, hydraulically operable reversible motor means, conduit means for supplying to and exhausting fluid from said motor means, a coarse fluid-control valve and a flne fluid-control valve included in said conduit mean for controlling the flow of fluid therethrough, and a pair of hydraulically operable valve means jointly operable when in one position thereof to connect said fine valve in controlling relation to said motor means but separately movable to second positions rendering said fine valve ineffective and connecting opposite sides, respectively, of said motor means to a source of fluid under pressure and the other side of said motor means to exhaust, the operation of said valve means being controlled by said coarse valve. 1

4. In a hydraulic control system, hydraulically operable, reversible motor means, a source of fluid under pressure, conduit means for supplying to and exhausting fluid from said motor means, a fine fluid-control means for controlling the flow of fluid to one side of said motor and the exhaust thereof from the other side, hydrau lically operable synchronizing means movable to a first position connecting said motor on one side directly with said source of fluid pressure and from said displaceable means.- a

, valve in controlling relation hydraulically operable, displaceable means for controlling the direction and rate of operation of "said servo, a source of fluid under pressure, means 'for supplying to and exhausting fluid fine fluid-control means for controlling the flow of fluid to one side of said displaceable means and the exhaust thereof from the other side, hydraulically operable synchronizing means movable to a first position connecting one side of said displaceable means directly with said source of fluid pressure and the other side thereof to exhaust and to a second position operatively connecting said fine fluid-control means in controlling relation to said displaceable means, and a coarse fluid-control means for controlling the operation of said synchronizing means.

6. In a hydraulic control system, hydraulically plying to and exhausting fluid from said motor means, a coarse fluid-control valve and a flne fluid-control valve operatively included in said system and means for effecting simultaneous operations thereof in unequal butconstant ratio magnitudes, and hydraulically operable means operatively connected to and controlled by said coarse valve for alternatively connecting said fine valve in controlling relation to said motor means and for connecting said motor to a source of fluid under pressure.

7. In a hydraulic control system, hydraulically operable reversible motor means, conduit means for supplying to and exhausting fluid from said motor means, a coarse fluid-control valve and a fine fluid-control valve operatively included in said system and means foreflecting simultaneous operations thereof in unequal but constant ratio magnitudes, and hydraulically operable synchronizing means including two independently movable valve elements, each thereof being movable to positions operatively connecting said fine to said motor, one of said elements being movable to alternative positions connecting said fine valve in controlling relation to said motor meansand, respectively, connecting a first side of said motor means to a source of fluid under pressure and the second side thereof to exhaust, and the other of said elements being movable to a position connecting said finevalve in controlling relation to said motor means and to a position connecting the second side of said motor means to a source of fluid under pressure and the first side thereof to exhaust, and rnwns controlled by said coarse valve means for controlling the flow of fluid therethrough, and fluid-pressure responsive means operatively connected with said coarse valve and including means responsive to fluid pressure supplied thereto through said coarse valve for renmined value and ineffective to control said mo-- tor means when the fluid pressure supplied from said coarse valve exceeds said predetermined value.

EDWARD DAWSON.

Number 16 REFERENCES crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date 2,058,642 Sperry Oct. 27, 1936 1,787,328 Schottler Dec. 30, 1930 2,260,979 Morin et a1 Oct. 28, 1941 2,283,397 Tucker May 19, 1942 1,943,061 Douglas Jan. 9,1934 1,481,645 Kaminski Jan.'22, 1924 2,160,779 Granst May 30, 1939 2, 9 ,792 H111 Feb. 27,1940 2,263,315

Rose Nov. 18,1941 

